1. Field of the Invention
The present invention relates to tank cleaning apparatus, and in particular, it relates to apparatus that automatically cleans the inside of a bulk milk storage tank in a sequence of automatically controlled cycles.
2. Description of the Prior Art
Milk on a dairy farm is stored in bulk cooling tanks until it is picked up for processing. The size of the tanks typically range from 300 to 3,500 gallons. The milk is picked up by the processor in a tank truck, typically, every other day or every day, depending on the size of the tank and the amount of milk being produced on the particular dairy farm. Regulations require that the interior surfaces of the storage tank be cleaned and sanitized each time the tank is emptied. Consequently, if the milk is picked up every other day, the tank must be cleaned every other day, and if the milk is picked up every day, the tank must be cleaned every day.
The cleaning of the milk storage tank is quite a chore since it requires at least three steps and sometimes four to satisfy the regulations and to insure that no stale or old milk has been left behind to contaminate the new incoming milk. The steps usually include a rinse, a detergent wash, an acid rinse, and an optional sanitizing step. A considerable amount of time is typically spent either handwashing the inside of the tank, or connecting washing equipment to the tank and monitoring the equipment during the various cycles.
There are several prior art patents which show various tank cleaning systems used for cleaning tanks on transport trucks which are of interest. They are:
Miller, U.S. Pat. No. 3,033,215, granted in May of 1962; Lyon, U.S. Pat. No. 3,188,238, granted in June of 1965; Metz, U.S. Pat. No. 3,825,022, granted in July of 1974; Reiter, U.S. Pat. No. 3,860,018, granted in January 1975
There are also several commercial devices presently on the market which clean bulk milk storage tanks in a plurality of cleaning cycles. Generally, each of the commercial systems includes a control cabinet wherein hot and cold water is mixed with an appropriate cleaning compound through a series of solenoid valves and then supplied either to a recirculating pump, or fed directly into the tank. A pump pumps the cleaning solution during each cycle through a spray nozzle that is positioned within the interior of the tank.
One such company is the Paul Mueller Company of Springfield, Mo. which manufactures a portable pump unit which has a spray nozzle which extends into the tank outlet from which milk is normally pumped. The cleaning fluid is supplied directly to the pump and sprayed within the tank. When a particular cycle ends, the tanks is drained by a diaphragm-type drain valve which operates on water pressure.
Two other commercial cleaning systems, the first manufactured by Sunset Equipment, St. Paul, Minn., and the other marketed by CP Division of St. Regis of Chicago, Ill., are also portable systems which have to be connected to the milk tank each time the milk tank has been emptied. These systems pump fluid into the interior of the tank through a spray device that is positioned proximate the top interior surface of the tank. A section of conduit is then attached to the outlet from which milk is normally emptied from the tank forming a closed loop recirculation system.
All of the above commercial cleaning systems have to be attached each time the milk tank is emptied which can occur every day or every other day. After cleaning, the systems have to be disconnected so that the milk tank is ready for the next milking. The systems of the prior art have been portable cleaning systems, since regulations in the storage and handling of milk are rather strict. The attachment and detachment of these cleaning systems increases the opportunity for contamination.
In addition, during the cleaning cycles, the fluid is normally drained on the floor of the milk house running into a floor drain. For this reason, the portable systems of the prior art also pose an electrical hazard since the electrical cords which operate the pumps and the electronic solenoid valves are typically lying on the floor.